The present invention relates generally to a liquid coating composition which comprises, as a binder, a compound containing at least two pendant activated unsaturated groups and, as a crosslinking agent for the activated unsaturated groups of the binder, a particular unblocked monoprimary amine.
A coating composition comprising, as a binder, a compound containing at least two pendant activated unsaturated groups and an amine crosslinking agent is generally known from EP-A-0203296 (equivalent to U.S. Pat. No. 4,990,577) and EP-A-0346982 (equivalent to U.S. Pat. No. 4,981,944) which are both incorporated by reference herein for all purposes. The amine crosslinking agent may contain only one primary amino group, but it is taught that this primary amino group must be blocked with, for example, an aldehyde or ketone.
As is well-known, the reactive groups of crosslinking agents are often blocked to prevent unwanted early reaction and, consequently, decreased potlife of the coating composition. Amine crosslinking agents normally are blocked with, for example, aldehydes and/or ketones.
The use of such blocking agents can have a number of disadvantages. For example, elevated temperatures are often required to unblock the crosslinking agents and, particularly for the above blocking agents, water is required to remove the aldehyde or ketone. With very low relative humidities, therefore, the cross-linking reaction can be delayed or proceed only very slowly. Further, once the crosslinking agent is unblocked, the blocking agent must be removed or it will remain in the coating composition as an impurity. This can lead to the previously applied coating, or the coated substrate itself (particularly plastics). being attacked.